A series of highly Er3+/Yb3+ co-doped fluoroaluminate glasses were investigated in order to develop a microchip laser at 1.54 μm under 980 nm excitation. Measurements of absorption, emission and up-conversion spectra were performed to examine the effect of concentration quenching on spectroscopic properties. In the glasses with Er3+ concentrations below 10% （mol fraction）, concentration quenching is low and the Er3+/Yb3+ co-doped fluoroaluminate glasses gave stronger fluorescence of 1.54 μm from the (（）4I13/2)→(（）4I15/2) transition than those of Er3+ singly-doped glasses. In the glass with Er3+ concentrations above 10%, concentration quenching of 1.54 μm obviously occurs more than that of the Er3+ singly-doped samples because of the back energy-transfer from Er3+ to Yb3+. To obtain the highest emission efficiency at 1.54 μm, the optimum doping-concentration ratio of Er3+/Yb3+ is found to be approximately 1∶1 in mol fraction when the Er3+ concentration is less than 10%.
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